Nexus 5548 vPC re-configuration

[uddika kahawatte]

hi community,

we have a "double side" vPC connecting 2 pairs of Nexus 5548 switches across two racks in the same data center. the plan is to move the one rack to another data center 20 km away, but to keep the existing setup the same.

present setup:

                   
+-----------+    vPC      +----------+
|           +-------------+          |
| nexus 5548|             |nexus 5548|
+-----------+----    -----+----------+
                 \  /
                  \/
                  /\
+-----------+----/  \-----+----------+
|           |             |          |
|nexus 5548 +-------------+nexus 5548|
+-----------+    vPC      +----------+
                   

would like to know if we can extend the links in the following way, across 2 x 4Gbps dark fiber links, by having the same configurations in place in the Nexus switches for the vPCs. instead of running 4 dark fiber links, we are planning to have just two dark fiber links and trunk 2 VLANs in each, to virtually provide the 4 existing physical links between the present Nexus switch setup.


new setup:
                     10 Gbps NTU                  10 Gbps NTU
                       +----+                      +----+
                       |    |      4 Gbps          |    |
+-----------+    vPC   |    +----------------------+    |    vPC     +----------+
|           +----------+    |    (2 x VLANs)       |    +------------+          |
| nexus 5548|          |    |                      |    |            |nexus 5548|
+-----------+---    ---+----+                      +----+------------+----------+
                \  /                                     
                 \/                                        
                 /\    +----+                      +----+              
+-----------+---/  \---|    |                      |    +------------+----------+
|           |          |    |                      |    |            |          |
|nexus 5548 +----------+    |        4 Gbps        |    +------------+nexus 5548|
+-----------+    vPC   |    +----------------------+    |    vpc     +----------+
                       |    |    (2 x VLANs)       |    |
                       +----+                      +----+
                     10 Gbps NTU                 10 Gbps NTU


by the way, we already have 4 x 10Gbps links forming double side vPC, but the link utilization between the data centers is less than 4 Gbps. so we assume that the new 2 x 4 Gbps bandwidth will be sufficient in terms of capacity.

i am more concerned about the configurations here.


thanks,

uddika

[Reza Sharifi]

Hi,

vPC configuration should not change since you are basically moving each vPC leg to a different physical location.The only thing that should change is the physical fiber from multi-mode to single mode. Since each leg of the vPC is 20 km apart, how are you planning to do vPC keep-alive?

HTH

[uddika kahawatte]

thanks for replying Reza, vPC keep-alive is only between the paired vPC switches, not between the two pairs. this is a double sided vPC setup where each 5548 pair sees the other pair as a single device connected by vPC. please confirm.

[Reza Sharifi]

Maybe I did not understand the question but let me ask again.

You have say nk5-1 and nk5-2 in a pair using vPC peer link and keep-alive and you also have nk5-3 and nk5-4 in another pair using another vPC with peer link and keep-alive.

You currently have full mesh connectivity between these 2 pairs.

So, you are planning to have nk5-1 and nk5-3 in building-a and nk5-2 and nk5-4 in building-b

Is that correct?

[uddika kahawatte]

hi Reza,

we are planning to have nk5-1 and nk5-2 in building-a and nk5-3 and nk5-4 in building-b

.

[Reza Sharifi]

Hi,

I understand it now. Each pair will stay in the same building. As for connectivity between the pairs, you need 4 links (fully meshed) in a vPC.  See figure-2 in this link:

http://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

HTH

[uddika kahawatte]

Hi Reza,

thank again, i am aware that we need 4 links, but we are just planning to have it via 2 physical trunks carrying 4 vlans (2 vlans in each trunk) where each vlan forms is a connection of the full mesh between the two 5k pairs. from the 5k switches point of view, these 4 vlans in the 10Gbps NTU are 4 x access ports to connect to the other pair.